Modeling the solvent effect, kinetics, morphology and catalysis in polymerization reactions

Abstract

In this dissertation, quantum chemical tools, in particular density functional theory (DFT), molecular dynamics (MD) and coarse-grained (CG) simulations are used to address the solvent e ect, kinetics, morphology and catalysis in polymerization reactions. The free-radical copolymerization kinetics of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) have been investigated by DFT in three di erent media (bulk, dimethylformamide (DMF), toluene). In DMF, the reactivity of the monomer HEMA, thereby its composition in the copolymer decreases because of the H-bonding tendency of the monomer with DMF. The e ect of Lewis acid coordination on the propagation kinetics and mechanism of N,N -dimethyl acrylamide (DMAM) has also modeled with DFT. It is shown that the terminal-monomer type of propagation is the most probable pathway favoring the isotactic product formation. A multiscale approach has been used to understand the morphological behavior of thermo-responsive polymer poly (2-isopropyl-2-oxazoline) (PIPOX) in aqueous solution. The most probable structure for the PIPOX chain above Tc is obtained by torsional analysis after reversemapping of the CG structure followed by MD simulations. X-ray di raction pattern well-reproduces the experimental one for crystalline PIPOX nanoribbons formed in water above Tc. The results are important in identifying a new helical conformation for PIPOX prior to crystallization. The mechanisms of cationic ring-opening polymerization of benzoxazines are still not well established. Reaction mechanisms giving phenoxy and phenolic type products have been modeled for pC-m monomer which is expected to give phenolic type product; the rearrangement mechanisms to obtain phenolic type products are also evaluated.